Television antenna



April 8, 1953 R. VRIDERMAN 2,636,986

TELEVISION ANTENNA Filed Oct. 11. 1948 2 SHEETS-SHEET 1 5 jmmnzm J 25@alj/MV/Ildil ow- Slams April 8, 1953 R. RIDERMAN 2,636,986

TELEVISION ANTENNA Filed Oct. 11. 1948 2 SHEETS-SHEET 2 3 WZbI/VMJPatented Apr. 28, 1953 TELEVISION ANTENNA Rudolph Riderman, Chicago,Ill., assignor, by mesne assignments, to Fred Gold, Chicago, Ill.

Application October 11, 1948, Serial No. 53,800

2 Claims. 1

This invention relates generally to antennas for the reception ortransmission of electrical radiation and more particularly is concernedwith antennas for the reception of high frequency broad. band radiation,such as for example, television.

It is known that an efiicient transmitting antenna will likewise be asatisfactory receiving antenna and vice-versa, hence, although my newantenna is primarily intended for reception it is nevertheless capableof being utilized for the transmission of television.

Present day television is broadcast at high frequencies in two generalbands, one of which is from 44 to 88 megacycles per second, and thesecond of which is from 1'74 to 216 megacycles per second. For any givenmetropolitan area, there are channels in both of these bands, andtherefore it is essential that an antenna be capable of receiving thevideo waves from transmitting stations operating in both bands.

.All of the antennas used for the reception of video waves haveheretofore been constructed in manners giving rise to objections whichhave considerably delayed the popularity of television, and hencelimited sales of reception equipment and the scope of the benefits to bederived from wide-spread use of television. It is the principal objectof my invention to attain the broad result of increased publicrecognition and acceptance of television by making it more economical,convenient, and desirable for the consumer to obtain, install, use, andenjoy a television receiving equipment.

The video frequency electric waves which are transmitted for receptionare considerably shorter" than ordinary radio waves. The long antennasof radio are therefore neither suitable nor.desirable in television.When frequencies of the order of 40 to 200 megacycles are to be receivedor transmitted, the amount of energy which can be radiated or receivedby a given antenna is wery small, and hence it is essential that suchantennas be directive. In addition, it is also desirable to utilize thebest attributes of an antenna in order to enable the maximum energy tobe transferred thereby, either from the transmitter to the ether, orfrom the ether to the receiver. The basic antenna for greatestefficiency, which may be considered an element, since most'antennas aremade up of such basic antennas, is a di-pole, or half-wave antenna. Asits name implies, such an antenna is constructed of a conductor half awave long. This electrical length is slightly less than the physicallength, and gives rise to current andvoltage distribution which is bestfor reception and transmission of high frequency energy. The existenceof this condition gives rise to a resonance in the antenna so that atthe center thereof, to which the lead-in transmission line is usuallysecured, there is a maximum of current and a minimum of voltage, and theimpedance of the antenna is practically pure resistance.

Considering the frequencies of the bands now being used for television,an antenna designed for best reception at the low end of the lower bandwould be of the order of eleven feet in length; at the high end ofthe'lower band would be of the order of five and one-half feet inlength; at the low end of the upper band would be of the order of 2.8feet in length; and at the high end of the higher band would be of theorder of 2.2 feet in length. Two compromises must be made in order toconstruct a television antenna which is suitable for reception over theentire range of both bands. One compromise must be made in each band inorder to choose a length which will be capable of receiving all of thechannels in that band, and then an overall compromise must be made sothat the antenna will receive stations from both bands. The net resulthas been that the common television antenna is of the order of three tosix feet in length.

A second type of antenna is one which has two sections, one forreceiving in each of the present day bands. In the event that there isan increase in allotted bands of the spectrum, another section will haveto be added to this antenna.

An important object of my invention is to provide a single antenna,capable of being tuned to any frequency over a wide range includingpresent day television bands.

A further object of my invention is to provide an antenna which iscapable of highly'eflicient reception by reason of the fact that theeffective length thereof can readily be adjusted to the frequency of thevideo signal being received over the entire television frequencyspectrum.

In order to achieve the maximum of eificiency it is best to install anantenna as high above ground as possible, hence television antennas arecustomarily installed on rooftops and towers. In addition, the size ofprior antennas makes it impractical to install same indoors. In crowdedcommunities there is objection to the installation of such antennas,whereby a tenant in an apartment building is deprived of the benefits oftelevision because he is not permitted to install an antenna upon theroof.

A further object of my invention is to provide a construction oftelevision antenna which is highly eiiicient and yet so small inphysical size that it is readily portable, can be installed indoors andin addition is extremely economical to manufacture.

My invention has given rise to many advantages over prior televisionantennas. It has eliminated the need for expensive outdoor weatherproofinstallations. Zt has eliminated the expense of maintenance of suchoutdoor antennas. It has eliminated the need for long transmission linesfrom the antenna to the receiver. It has enabled the antenna, by reasonof its being immediately adjacent the receiver, to be made revolvable sothat the maximum directional response can be obtained merely by manualorientation of the antenna. Obviously, rooftop antennas cannot be maderevolvable without the use of highly expensive equipment.

My new antenna can be placed immediately adjacent the receivingequipment and can be constructed so that it is ornamental in appearanceso as not to detract from the esthetic effect of the furnishings in agiven room. The elimination of long lengths of transmission line byreason or" the location of my new antenna makes better receptionpossible. In cases where the line is not perfectly matched to theantenna, standing waves are set up which give rise to blurring of thevideo picture, and sometimes to ghosts.

The shorter the transmission line, the less is the effect of thesestanding waves. My invention enables transmissions lines to be of theorder of inches in length. Short transmission lines also decrease lossof signal due to attenuation, and decrease noise pick-up In the case oftelevision installations where the antenna is a substantial distancefrom the receiving equipment, there may exist a phase difference betweenthe signal received directly at the receiver and that received from theantenna via the transmission line, giving rise of blurring or ghosts.This fault can be corrected by shielding the receiver, an expedientunnecessary in case my new antenna is used.

Certain objects of my invention lie in the provision of an antenna whoseelectrical length isconsiderably greater than its physical length; toprovide a broad band antenna for indoor use;

to provide an antenna in which inductive reactance for loading theantenna. is distributed along the same; to provide an antenna in whichthe inductive reactance is capable of readily being varied; tov providean antenna having, an inductive. reactance. coil associated therewithin. such a manner that telescopically moving same with respect toanother portion of the antenna will vary the inductive effect of such.coil; to provide an antenna which can readily be adjusted. for optimumtuning. and matching.

With the foregoing: and. other objects in. View which will appear as thedescription proceeds. the invention consists of. certain novel. featuresof construction, arrangement and a combination of. parts hereinafterfully described, illustrated. in. the accompanying drawings, andparticularly pointed out in. the appended claims, it being. un--derstood that various changes. in the form,v proportion, size and minordetails.- of the structure may bev made without. departing from. the.spirit or sacrificing any of the advantages. of! the invention- For thepurpose. of facilitating an. understand-- ing of this invention, thereis. illustrated in the. accompanying drawings. a preferred embodimentthereof, from an inspection of which, when considered in connection withthe following description, this invention, its mode of construction,assembly and operation, and many of its advan tages should be readilyunderstood and appreciated.

Referring to the drawings in which the same characters of reference areemployed to indicate correspondence or similar parts throughout theseveral figures of the drawings:

Fig. 1 is a perspective view of an antenna embodying my new invention.

Fig. 2 is a top plan view of the same.

Fig. 3 is a side elevational view of the antenna.

Fig. 4 is an end elevational View of the antenna.

Fig. 5 is a fragmentary sectional view through the antenna taken alongthe axis of the antenna di-pole as indicated by the line 5-5 of Fig. 3and in the indicated direction, and showing the details of constructionof the antenna coil.

Fig. 6 is a sectional view throughthe antenna di-pole along the axisthereof as indicated by line 6-5 of Fig. 3, in the direction indicated.

Fig. 7 is a sectional view taken along the line 'E-l of Fig. 2 and inthe indicated direction.

Fig. 8 is a top plan view of a modified form antenna embodying myinvention.

For carrying out my invention I have provided an antenna, a part ofwhich consists of a tubular conductor, preferably circular incross-section although not limited thereto, having a second part formedof a telescoping member of slightly lesser cross section, but having acoil of bare wire wound thereon. The coil form is of some materialhaving high dielectric strength, and the winding is laid on the form,preferably in grooves, so that it extends out of the grooves, andengages the inner surface of the tubular conductor whereever the form istelescoped therein. The windings are spaced apart in order to distributethe inductance along the form and to provide a wide area capable ofcutting the incident video waves. In this manner I am enabled toincrease the eiiective or eiectrical length of my antenna by addinginductive reactance thereto, but in addition I have distributed thecoiled conductor along the coil formed thereby increasing the amount ofenergy the antenna is capable of extracting from the transmitted videowave.

My preferred embodiment includes a di-pole having two tubular centralsections arranged with their axes aligned and their ends spaced andconnected to the lead-in transmission line, and having coils telescopedinto the free ends thereof. A modified form has the central portion ofthe di-pole formed of coils, while the ends of the coils are capped withtelescoping cylindrical sleeves.

For any given frequency, I adjust the antenna for maximum signal andbest matching of trans mission line impedance by telescopically movingthe coils and tubes relative to one another.

The reference character it! designates generally a platform which maycomprise a fixed member, the top of a receiving equipment, a. table, orthe like, and is not. necessarily circular in formation as shown in thedrawings. Mounted upon. the platform. [iii II have provided a turntablel l separated from. the platformv ill by a suitable bearing member orwasher. l2 and pivoted thereto by means of a. bushing [3 (see Fig- 7.)having. a. flanged upper end as shown. at i l overlying. the turntable.I. i'. This construction enables theturntable. to. be rotated although.same can be lifted upwardly carrying. the bushing 43 therewith. If

desired the bushing l3 may have its lower end peened over and againstthe bottom of the platform Ill whereby permanently to associate sametherewith and prevent removal of the turntable.

Centrally of the bushing there is provided an insulating member l5cylindrical in formation, and having a bore l6 through which thetransmission line I! is adapted to pass.

Mounted upon the turntable II I provide a di-pole antenna designatedgenerally I8, and a parasitic antenna designated generally l9. Both ofthese antennas are adjustable as to their physical length, and thedistance therebetween is also adjustable as will be described.

The di-pole antenna consists of a pair of thinwalled tubes ZEI and 2|arranged with their ends juxtaposed and their axes aligned. There is aspace 22 between the ends whereby the tubes and 2| do not touch.

The tubes 26 and 2| are firmly mounted upon stand-off insulators 23 and24 formed of some material having very high dielectric strength, such asfor example polystyrene, or methyl methacrylate resin. These insulators23 and 24 are in turn mounted upon the turntable I by means of screws 25which are engaged into the bottoms of the stand-off insulators throughslots 26 and 21 for a purpose presently to be described. The means formounting the tubes 20 and 2| upon tr. e insulators 23 and 24 may consistof any suitable fasteners such as for example the bolts shown at 28 and29 which I have welded to the bottoms oi. the tubes 20 and 2|respectively.

Telescopically mounted within the tubes 20 an :1 2| I provide the coils30 and 3| respectively. These coils consist of relatively heavy diameterwire 32 wound upon tubular forms 33 of polystyrene or similar insulatingmaterial. In the embodiment shown, the wire 32 is laid in spiral grooves34 cut in the surface of the forms, the depth of the grooves 34 beingsuch that the turns of the wire 32 protrude slightly therefrom, andhence rise above the exterior surface 35 of the forms 33. Both formsused in the coils 30 and 3| are identical, hence the description of coil30 illustrated in Fig. 5 should suflice. The ends of the wire 32 areinserted through openings 36 formed in each end of each form 33 and bentunder as shown at 31 on the interior of each form in order to hold thewindings in place.

From the above description it should be obvious that the coils 30 and 3|are readily slidable within the tubes 20 and 2|, and that when the coilsare engaged within said tubes 20 and 2|, the

outside diameter ofthe coils comprising the outi ermost surface of thewindings will engage the inner surface of the tubes 20 and 2|, givingrise to a metal to metal contact.

The tubes 20 and 2| are provided with contacts at 38 and 39 adapted tobe connected respectively to the wires of the transmission line H.Obviously the line I! should have animpedance matching that of theantenna.

I have thus far described the important portion of my invention and itwill be seen that it consists of a di-pole antenna having distributedinductance therealong. The coils 30 and 3| provide inductance, and byarranging the coils so that their axes are aligned with those of thetubes 20 and 2| I have provided a physical antenna di-pole as well asinductance. The efficiency of such an antenna is greater than a shortantenna having lumped inductive loading because the coils 30 and 3| arealso in the electrostatic and electromagnetic fields of the video 6waves and are enabled thereby to extract addi tional energy therefrom.

The antenna illustrated utilizes cylindrical tubes having a diameter ofapproximately two inches, whereby the antenna can receive broad band offrequencies without the discrimination against any portion of a channel.The effect accompanying such construction is a reduction of signalpick-up from the incident waves, but the coils 30 and 3| having addedconsiderable inductance, the loss due to reduced Q is not as great as itotherwise would be.

Many advantages accrue as a result of the arrangement that I havedescribed, irrespective of the construction including the turntable andadjustable stand-oil insulators. The necessity of using a large andunwieldy antenna is eliminated thereby enabling the entire antenna to bemaintained within the room containing the receiving set. In the case oftelevision receiving sets, my new antenna is so small that it can bemounted immediately upon the top of the cabinet of the televisionreceiving set, thereby reducing transmission line length, cost, andlosses. In addition to the above, since the antenna is immediatelyavailable to the observer, the same may be rotated so that it isproperly oriented for maximum reception, that is, with the axis of theantenna dipole at right angles with a line from the transmittingstation. In permanently mounted antennas, this cannot be done unless theinstalla tion is highly complicated, and consequently very expensive.With my new invention, the observer merely rotates the antenna turntableuntil optimum signal is obtained. Permanently mounted antennas must beoriented so that the direction in which they are arranged for receptionis a resultant of directions of all the stations it is desired toreceive. In such case, it is obvious that the signal to noise ratio forsome stations may be prohibitive. Obviously, the great advantages ofhaving a highly directive receiving antenna are lost if the antenna mustbe designed to remain fixed.

The advantage of ready orientation is achieved by reason of the antennabeing so small as to readily be mountable in the immediate vicinity ofthe receiving equipment so as to be capable of manipulation by theobserver. In addition to this, other great advantages accrue. Thus, permanently mounted antennas require tuning cir cuits in order to causesame efiiciently to receive all stations, since their physical sizecannot readily be varied. On the other hand, my new antenna has meansfor tuning the antenna by varying the physical size as well as adjustingthe distributed inductance thereof so that the optimum effective lengthof the antenna can immediately be achieved for any given station andcondition of reception. The manner of accomplishing this will beexplained hereinafter.

The coils 30 and 3| of my antenna are capable of being moved in and outof the tubes 20 and'2l by the observer. The turns of the coils that areenclosed within the tubes are short circuited since the wire 32 thereofis in engagement with the inner surface of the said tubes. This not onlydecreases the physical length of the di-pole antenna that cuts the videowaves, but as well decreases the inductance of the coils 30 and 3|, andhence further decreases the effective length of the antenna. Obviously,not only is the antenna readily tunable, but it is readily tunable overan extremely wide range of frequencies so that it i its simple matter totune the antenna to any station in the presently used television bands.

although manual movement of the coils is described herein, it should beobvious that any method of moving said coils, mechanically orelectrically could be used, and in addition, the exact position of saidcoils for certain frequently received stations coul be calibratedthereon, or otherwise indicated. In addition the azimuth may be markedupon turntable II to properly orient the antenna.

It is Well known that the directivity of antennas can be improved by theuse of parasitic antennas. 1 have consequently determined that theefficienc'y' of my new antenna is greatly increased by the use of aparasitic antenna serving as" a reflector to cause the antenna to beunidirectional. I have therefore mounted a parasit ic antenna 9 to therear of di-pole i8, and have provided for adjustment of the distancebetween the antennas by means of the screws 25 and the slots 2t and 2?.The distance between antennas can thus be adjusted to one tenth the wavelength of the received frequency, or whatever is optimum. This dimensionis not critical, however, especially in the case of broad band receptionwhere the thickness of the antenna proper is of the order of thatdimension, and hence adjustment between the parasitic and dipoleantennas may be eliminated, or the antenna may be adjusted for bestreception over the entire band, and then fixed.

The parasitic antenna consists of a fixed central tube 59 mounted upon astandoff insulator 5i and having telescoping tubes 52 and 53 on the endsthereof. This provides for tuning of the parasitic antenna i9. This typeof parasitic antenna acts as a reflector, serving to pick up additionalenergy from the passing video waves and reflect at proper phase into thedipole It.

It will be noted that the coils 3i) and 31 are not directly connected.to the transmission line [1. They are each produced as a unit and thentelescoped into respective tubes 2c and 2!. enables shipping the antennain a small container.

in Fig. 8 I have shown a modification of my invention which reverses thepositions of the coils and tubes of the antenna heretofore described.The efiiciency of such antenna and the advantages are generally the sameasv those of the antenna described. In the modified form of antenna thetubes 20 and 2! are formed as sleeves so and 6! which slide over theends of the coils 62 and 83 respectively. The coils are both mountedupon a single form E l which is attached to the turntable H, and eachhas its inner terminus connected with the transmission line ii as shownat 65 and 6B. In all other respects the device is the same as describedand is turnable in the same manner.

Although the parasitic antenna has been shown This constructed fromtubing it should be obvious that same could also be formed of coils andtubes in the same manner as I form my di-poles. In addition, for highimpedance transmission lines, various combinations of coils and tubescould be arranged in the form of a folded dipole to provide increasedantenna impedance.

It is believed that this invention, its mode of construction andassembly, and many of its advantages should be readily understood fromthe foregoing Without further description, and it should also bemanifest that while a preferred embodiment of the invention has beenshown and described for illustrative purposes, the structural detailsare nevertheless capable of wide variation within the purview of thisinvention as defined in the appended claims.

What is claimed and desired to be secured by Letters Patent of theUnited States is:

1. A broad band television receiving antenna comprising horizontallyarranged driven and parasitic elements spaced one in back of the otherwith their axes parallel and both perpendicular to the direction of theincident waves, the driven element comprising a pair of hollow metalliccylindrical tubes with a common axis, spaced one from the other alongthe axis and rigidly supported in such spaced position, a rotatablestandard mounting said tubes, lead-in means electrically connected tosaid tubes to transmit the signal received when same are resonating asthe halves of a dipole, each tube having a telescoping member in theouter end thereof, said member being formed of insulating material andhaving Wire helically arranged on the exterior thereof so that as themember is moved in and out of the respective tube, the tube will shortcircuit or uncover turns to tune the dipole, said parasitic elementbeing a hollow cylindrical metal tube electrically continuous along itslength secured to said standard and insulated therefrom.

2. A construction as described in claim 1 in which the parasitic elementis formed of a central fixed cylindrical tube, and the ends thereof areformed as adjustably telescoped tubes in metallic contact therewith.

RUDOLPH RIDERMAN.

References Cited in the file of this patent UNITED STATES PATENTS Number

